Historically, propellant tanks for liquid rockets have been manufactured using metal. Recently, composite tanks made using, for example, graphite or epoxy have been used for storable propellants such as kerosene and as high pressure tanks in order to reduce their structural weight, and thus the overall weight of dependent systems.
Liquid oxygen (LOX), a cryogenic propellant, is one of the most efficient oxidizers from a mass and performance aspect. Other cryogenic propellant fuels include liquid hydrogen and liquid methane. There has been no successful demonstration of cryogenic propellants such as LOX in a high-pressure composite tank. Most composite tank failures using LOX can be attributed to microcracking of the composite resin matrix due to large differences in the coefficient of thermal expansion (CTE) between fibers and the resin used to manufacture such tanks. Also, there are no known resins that won't microcrack under these conditions.